A standard optical disk is made between a pair of mold parts, one of which has a surface that embosses in the resin the disk is made from bumps that carry the disk's data. The hot resin may be cured with ultraviolet light. Once the disk is formed, the mold is opened, invariably leaving the disk stuck to the mold part having the data-forming bumps.
Stripping the disk from the mold is a fairly delicate task because the still-hot disk is extremely fragile, and also because the data-carrying formations are very minute. At the same time the disk must be handled with reasonable speed to free the mold to make another disk, as the molds are so very expensive that they cannot be left idle. Using a suction-type lifter or gripper is one proposed method that frequently spoils the somewhat soft disk.
German patent document 2,917,042 filed Apr. 27, 1979 by Gunther Schauffeld (citing U.S. Pat. Nos. 4,124,352 and 3,830,613) describes a system where a punch physically knocks a molded workpiece out of a mold. Such an arrangement is fairly crude and, indeed, this patent document does not deal with a delicate optical disk but with a more rugged workpiece.
In German patent document 3,027,568 filed by Egbert Broeksoma et al with a claim to a Dutch priority date of Aug. 10, 1979 an arrangement is described whereby grippers engage the edges of an optical disk and peel it off one of the mold parts after it has cured somewhat. This arrangement deforms the disk considerably and can, therefore, damage it.
PCT publication WO 88/01564 (citing U.S. Pat. Nos. 4,519,767, 4,283,973, and 4,441,949) also grips the edges of the disks as they are being processed, but does not describe how the disks are stripped from the mold they are originally produced in.
Finally, European patent application publication 339,616 injects air between the disk and the mold part it is stuck to to free it therefrom. This procedure is relatively gentle, but still does substantially deform the disk so that it can be damaged, especially as it is still fairly hot and plastically deformable when it is being separated from the mold.